The planet mercury makes one rotation. Planets of our solar system

Mercury is the closest planet to the Sun in the Solar System, orbiting the Sun in 88 Earth days. The duration of one sidereal day on Mercury is 58.65 terrestrial, and solar - 176 terrestrial. The planet is named after the ancient Roman god of commerce Mercury, an analogue of the Greek Hermes and Babylonian Naboo.

Mercury belongs to the inner planets, as its orbit lies within the Earth's orbit. After Pluto was deprived of its planetary status in 2006, the title of the smallest planet in the solar system passed to Mercury. The apparent magnitude of Mercury ranges from 1.9 to 5.5, but it is not easy to see due to its small angular distance from the Sun (maximum 28.3 °). So far, relatively little is known about the planet. Only in 2009, scientists compiled the first complete map of Mercury, using images from the Mariner 10 and Messenger vehicles. The planet has not been found to have any natural satellites.

Mercury is the smallest planet in the terrestrial group. Its radius is only 2439.7 ± 1.0 km, which is less than the radius of Jupiter's moon Ganymede and Saturn's moon Titan. The mass of the planet is 3.3 1023 kg. The average density of Mercury is quite high - 5.43 g / cm, which is only slightly less than the density of the Earth. Given that the Earth is larger in size, the density value of Mercury indicates increased content in its bowels of metals. Free fall acceleration on Mercury is 3.70 m / s. The second space velocity is 4.25 km / s. Despite its smaller radius, Mercury still surpasses the mass of such satellites of giant planets such as Ganymede and Titan.

The astronomical symbol of Mercury is a stylized image of the winged helmet of the god Mercury with his caduceus.

Planet movement

Mercury moves around the Sun in a rather highly elongated elliptical orbit (eccentricity 0.205) at an average distance of 57.91 million km (0.387 AU). At perihelion, Mercury is 45.9 million km from the Sun (0.3 AU), at aphelion - 69.7 million km (0.46 AU) At perihelion, Mercury is more than one and a half times closer to Sun than aphelion. The inclination of the orbit to the plane of the ecliptic is 7 °. For one revolution in orbit, Mercury spends 87.97 Earth days. The average speed of the planet in orbit is 48 km / s. The distance from Mercury to Earth varies from 82 to 217 million km.

For a long time, it was believed that Mercury is constantly facing the Sun by the same side, and one revolution around the axis takes it the same 87.97 Earth days. Observations of details on the surface of Mercury did not contradict this. This misconception was due to the fact that the most favorable conditions for observing Mercury are repeated after a period approximately equal to six times the rotation period of Mercury (352 days), therefore, approximately the same area of \u200b\u200bthe planet's surface was observed at different times. The truth was revealed only in the mid-1960s, when the radar of Mercury was carried out.

It turned out that the Mercury sidereal days are equal to 58.65 Earth days, that is, 2/3 of the Mercury year. Such a commensurability of the periods of rotation around the axis and the revolution of Mercury around the Sun is a phenomenon unique to the solar system. It is presumably explained by the fact that the tidal action of the Sun took away the angular momentum and slowed down the rotation, which was initially faster, until both periods were connected by an integer ratio. As a result, in one Mercurian year, Mercury manages to turn around its axis by one and a half revolutions. That is, if at the time of the passage of perihelion by Mercury a certain point of its surface is directed exactly to the Sun, then at the next passage of the perihelion exactly the opposite point of the surface will be directed to the Sun, and after another Mercury year the Sun will return to the zenith above the first point. As a result, a solar day on Mercury lasts two Mercury years or three Mercury sidereal days.

As a result of such a movement of the planet, it is possible to distinguish "hot longitudes" on it - two opposite meridians, which are alternately facing the Sun during the passage of the perihelion by Mercury, and on which it is especially hot because of this, even by Mercury standards.

There are no seasons on Mercury like on Earth. This is due to the fact that the planet's axis of rotation is at right angles to the orbital plane. As a consequence, there are areas near the poles that the sun's rays never reach. A survey by the Arecibo radio telescope suggests that there are glaciers in this cold and dark zone. The glacial layer can reach 2 m and is covered with a layer of dust.

The combination of planetary movements gives rise to another unique phenomenon. The speed of rotation of the planet around the axis is practically constant, while the speed of orbital motion is constantly changing. In the orbital section near the perihelion for about 8 days, the angular velocity of the orbital motion exceeds the angular velocity of the rotational motion. As a result, the Sun in the sky of Mercury stops and begins to move in reverse direction - from west to east. This effect is sometimes called the Joshua effect, after the main character of the Book of Joshua from the Bible, who stopped the movement of the Sun (Joshua 10: 12-13). For an observer at longitudes 90 ° from "hot longitudes," the Sun rises (or sets) twice.

It is also interesting that, although Mars and Venus are the closest in orbits to the Earth, Mercury is more often than others the planet closest to the Earth (since others are more distant, not being so "attached" to the Sun).

Anomalous orbital precession

Mercury is close to the Sun, therefore the effects of general relativity are manifested in its motion to the greatest extent among all the planets of the solar system. Already in 1859, the French mathematician and astronomer Urbain Le Verrier reported that there is a slow precession of the orbit of Mercury, which cannot be fully explained based on the calculation of the influence of known planets according to Newtonian mechanics. The perihelion precession of Mercury is 5600 arc seconds per century. Calculating the influence of all other celestial bodies on Mercury according to Newtonian mechanics gives a precession of 5557 arc seconds per century. Trying to explain the observed effect, he suggested that there is another planet (or, perhaps, a belt of small asteroids), the orbit of which is closer to the Sun than Mercury, and which introduces a disturbing influence (other explanations considered the unaccounted for polar contraction of the Sun). Due to the previously achieved successes in the search for Neptune, taking into account its influence on the orbit of Uranus, this hypothesis became popular, and the desired hypothetical planet even received the name Vulcan. However, this planet was never discovered.

Since none of these explanations have stood the test of observations, some physicists began to put forward more radical hypotheses that it is necessary to change the law of gravitation itself, for example, to change the exponent in it or add terms depending on the speed of bodies to the potential. However, most of these attempts have proven to be controversial. At the beginning of the 20th century, general relativity provided an explanation for the observed precession. The effect is very small: the relativistic "addition" is only 42.98 arc seconds per century, which is 1/130 (0.77%) of the total precession speed, so it will take at least 12 million revolutions of Mercury around the Sun for the perihelion to return into the position predicted by the classical theory. A similar, but smaller displacement exists for other planets - 8.62 arc seconds per century for Venus, 3.84 for Earth, 1.35 for Mars, as well as asteroids - 10.05 for Icarus.

Hypotheses of the formation of Mercury

Since the 19th century, there has been a scientific hypothesis that in the past Mercury was a satellite of the planet Venus, which was later "lost" by it. In 1976 by Tom van Flandern (eng.) Russian. and K.R. Harrington, on the basis of mathematical calculations, it was shown that this hypothesis explains well the large deviations (eccentricity) of the orbit of Mercury, its resonant nature of revolution around the Sun and the loss of rotational moment in both Mercury and Venus (the latter also - the acquisition of rotation opposite to the main one in the solar system).

At present, this hypothesis is not supported by observational data and information from automatic stations of the planet. The presence of a massive iron core with a large amount of sulfur, the percentage of which is higher than that of any other planet in the solar system, the features of the geological and physicochemical structure of the surface of Mercury indicate that the planet was formed in the solar nebula independently of other planets, that is Mercury has always been an independent planet.

Now there are several versions to explain the origin of the huge core, the most common of which suggests that Mercury originally had the ratio of the mass of metals to the mass of silicates similar to those in the most common meteorites - chondrites, the composition of which is generally typical for solids The solar system and the inner planets, and the mass of the planet in ancient times was approximately 2.25 times its true mass. In the history of the early solar system, Mercury may have collided with a planetesimal of about 1/6 of its own mass at a speed of ~ 20 km / s. Most of the crust and the upper layer of the mantle were blown into outer space, which shattered into hot dust and scattered in interplanetary space. And the core of the planet, consisting of heavier elements, has been preserved.

According to another hypothesis, Mercury was formed in the inner part of the protoplanetary disk already extremely depleted in light elements, which were swept out by the Sun into the outer regions of the Solar system.

Surface

In its physical characteristics, Mercury resembles the Moon. The planet has no natural satellites, but it has a very rarefied atmosphere. The planet has a large iron core, which is the source of the magnetic field in its entirety making up 0.01 of the earth's. The core of Mercury makes up 83% of the entire volume of the planet. The temperature on the surface of Mercury ranges from 90 to 700 K (from +80 to +430 ° C). The solar side warms up much more than the polar regions and the far side of the planet.

The surface of Mercury also resembles the lunar in many ways - it is heavily cratered. The density of craters is different in different areas. It is assumed that the more densely cratered areas are older, and the less densely covered areas are younger, formed by flooding of the old surface with lava. At the same time, large craters are less common on Mercury than on the Moon. The largest crater on Mercury is named after the great Dutch painter Rembrandt and is 716 km across. However, the similarity is incomplete - formations are visible on Mercury that are not found on the Moon. An important difference between the mountainous landscapes of Mercury and the Moon is the presence on Mercury of numerous jagged slopes stretching for hundreds of kilometers - scarps. The study of their structure showed that they were formed during compression, accompanying the cooling of the planet, as a result of which the surface area of \u200b\u200bMercury decreased by 1%. The presence of well-preserved large craters on the surface of Mercury suggests that over the past 3-4 billion years there has been no large-scale movement of crustal areas, and there was no erosion of the surface, the latter almost completely excludes the possibility of any significant existence in the history of Mercury. atmosphere.

During the research carried out by the Messenger probe, over 80% of the surface of Mercury was photographed and it was revealed that it is homogeneous. In this, Mercury is not similar to the Moon or Mars, in which one hemisphere differs sharply from the other.

The first data on the study of the elemental composition of the surface using the X-ray fluorescence spectrometer of the Messenger apparatus showed that it is poor in aluminum and calcium in comparison with the plagioclase feldspar characteristic of the continental regions of the Moon. At the same time, the surface of Mercury is relatively poor in titanium and iron and rich in magnesium, occupying an intermediate position between typical basalts and ultrabasic rocks such as terrestrial komatiites. A comparative abundance of sulfur has also been found, suggesting reductive conditions for planetary formation.

Craters

Craters on Mercury range in size from small, bowl-shaped depressions to multi-ring impact craters hundreds of kilometers across. They are in different stages of destruction. There are relatively well-preserved craters with long beams around them, which were formed as a result of the release of matter at the time of impact. There are also heavily destroyed remains of craters. Mercury craters differ from lunar craters in that the area of \u200b\u200btheir cover from the ejection of matter upon impact is smaller due to the greater gravity on Mercury.

One of the most noticeable features of the surface of Mercury is the Plain of Heat (Latin Caloris Planitia). This detail of the relief got its name because it is located near one of the "hot longitudes". Its diameter is about 1550 km.

Probably, the body, upon impact of which the crater was formed, had a diameter of at least 100 km. The impact was so strong that seismic waves, passing the entire planet and focusing on the opposite point of the surface, led to the formation of a kind of crossed "chaotic" landscape here. The force of the impact is also evidenced by the fact that it caused the release of lava, which formed high concentric circles at a distance of 2 km around the crater.

The point with the highest albedo on the surface of Mercury is the Kuiper crater, 60 km in diameter. This is probably one of the "youngest" large craters on Mercury.

Until recently, it was assumed that in the bowels of Mercury there is a metal core with a radius of 1800-1900 km, containing 60% of the planet's mass, since the Mariner-10 spacecraft detected a weak magnetic field, and it was believed that a planet with such a small size could not have liquid kernels. But in 2007, Jean-Luc Margot's group summed up the results of five years of radar observations of Mercury, during which they noticed variations in the planet's rotation, too large for a model with a solid core. Therefore, today we can say with a high degree of confidence that the core of the planet is precisely liquid.

The percentage of iron in the core of Mercury is higher than that of any other planet in the solar system. Several theories have been proposed to explain this fact. According to the theory most widely supported in the scientific community, Mercury originally had the same metal-to-silicate ratio as a normal meteorite, with a mass 2.25 times its current mass. However, at the beginning of the history of the solar system, a planet-like body hit Mercury, having a mass 6 times smaller and several hundred kilometers across. As a result of the impact, most of the original crust and mantle were separated from the planet, due to which the relative proportion of the core in the planet's composition increased. A similar process, known as the giant collision theory, has been proposed to explain the formation of the moon. However, the first data on the study of the elemental composition of the surface of Mercury using the AMS Messenger gamma-spectrometer do not confirm this theory: the abundance of the radioactive isotope potassium-40 of the moderately volatile chemical element potassium in comparison with the radioactive isotopes thorium-232 and uranium-238 of the more refractory elements uranium and thorium does not fit with high temperaturesunavoidable in a collision. Therefore, it is assumed that the elemental composition of Mercury corresponds to the primary elemental composition of the material from which it was formed, close to enstatite chondrites and anhydrous cometary particles, although the iron content in the enstatite chondrites studied to date is insufficient to explain the high average density of Mercury.

The core is surrounded by a 500-600 km thick silicate mantle. According to data from "Mariner-10" and observations from the Earth, the thickness of the planet's crust ranges from 100 to 300 km.

Geological history

Like the Earth, the Moon, and Mars, the geological history of Mercury is divided into eras. They have the following names (from earlier to later): pre-Tolstovskaya, Tolstovskaya, Kalor, late Kalor, Mansur and Kuiper. This division periodizes the relative geological age of the planet. Absolute ages, measured in years, are uncertain.

After the formation of Mercury 4.6 billion years ago, there was an intense bombardment of the planet by asteroids and comets. The last violent bombardment of the planet took place 3.8 billion years ago. Some regions, for example, the Plain of Heat, were also formed due to their filling with lava. This led to the formation of smooth planes inside the craters, like lunar ones.

Then, as the planet cooled and shrank, ridges and rifts began to form. They can be observed on the surface of larger features of the planet's relief, such as craters, plains, which indicates a later time of their formation. The period of volcanism on Mercury ended when the mantle collapsed enough to prevent lava from escaping to the planet's surface. This probably happened in the first 700-800 million years of its history. All subsequent changes in the relief are caused by impacts of external bodies on the surface of the planet.

A magnetic field

Mercury has a magnetic field, the intensity of which is 100 times less than the earth's. The magnetic field of Mercury has a dipole structure and in the highest degree symmetrically, and its axis deviates only 10 degrees from the axis of rotation of the planet, which imposes a significant restriction on the range of theories explaining its origin. Mercury's magnetic field is possibly formed as a result of the dynamo effect, that is, the same as on Earth. This effect is the result of the circulation of the planet's liquid core. Due to the pronounced eccentricity of the planet, an extremely strong tidal effect occurs. It keeps the core in a liquid state, which is necessary for the dynamo effect to manifest.

Mercury's magnetic field is strong enough to change the direction of the solar wind around the planet, creating a magnetosphere. The planet's magnetosphere, while small enough to fit inside the Earth, is powerful enough to capture the solar wind plasma. Observation results obtained by Mariner 10 have detected low-energy plasma in the magnetosphere on the planet's night side. Explosions of active particles were detected in the tail of the magnetosphere, which indicates the dynamic qualities of the planet's magnetosphere.

During the second flyby of the planet on October 6, 2008, Messenger discovered that the magnetic field of Mercury can have a significant number of windows. The spacecraft encountered the phenomenon of magnetic vortices - intertwined magnetic field knots that connect the spacecraft to the planet's magnetic field. The vortex reached 800 km across, which is a third of the planet's radius. This vortex form of the magnetic field is created by the solar wind. As the solar wind flows around the planet's magnetic field, it binds and sweeps with it, curling into vortex-like structures. These vortices of magnetic flux form windows in the planetary magnetic shield through which the solar wind penetrates and reaches the surface of Mercury. The process of linking planetary and interplanetary magnetic fields, called magnetic reconnection, is a common occurrence in space. It also occurs near the Earth when it generates magnetic vortices. However, according to the observations of "Messenger", the frequency of reconnection of the magnetic field of Mercury is 10 times higher.

Conditions on Mercury

The proximity to the Sun and the rather slow rotation of the planet, as well as the extremely weak atmosphere, lead to the fact that the sharpest temperature changes in the Solar System are observed on Mercury. This is also facilitated by the loose surface of Mercury, which conducts heat poorly (and with a completely absent or extremely weak atmosphere, heat can be transferred into the interior only due to thermal conductivity). The planet's surface quickly heats up and cools down, but already at a depth of 1 m, daily fluctuations cease to be felt, and the temperature becomes stable, equal to approximately +75 ° C.

The average temperature of its daytime surface is 623 K (349.9 ° C), at night - only 103 K (170.2 ° C). The minimum temperature on Mercury is 90 K (183.2 ° C), and the maximum reached at noon at "hot longitudes" when the planet is near perihelion is 700 K (426.9 ° C).

Despite such conditions, there have recently been suggestions that ice may exist on the surface of Mercury. Radar studies of the circumpolar regions of the planet have shown the presence of depolarization areas there from 50 to 150 km; the most likely candidate for a matter reflecting radio waves may be ordinary water ice. Coming to the surface of Mercury when comets hit it, water evaporates and travels around the planet until it freezes in the polar regions at the bottom of deep craters, where the Sun never looks, and where ice can persist for almost unlimited time.

When the spacecraft "Mariner-10" flew past Mercury, it was established that the planet has an extremely rarefied atmosphere, the pressure of which is 5 · 1011 times less than the pressure of the earth's atmosphere. Under such conditions, atoms are more likely to collide with the planet's surface than with each other. The atmosphere is made up of atoms captured from the solar wind or knocked out by the solar wind from the surface - helium, sodium, oxygen, potassium, argon, hydrogen. The average lifetime of an individual atom in the atmosphere is about 200 days.

Hydrogen and helium probably enter the planet with the solar wind, diffuse into its magnetosphere, and then go back into space. The radioactive decay of elements in Mercury's crust is another source of helium, sodium and potassium. Water vapor is present, released as a result of a number of processes, such as impacts of comets on the planet's surface, the formation of water from the hydrogen of the solar wind and oxygen from rocks, sublimation from ice, which is located in permanently shaded polar craters. Finding a significant number of water-related ions, such as O +, OH + H2O +, came as a surprise.

Since a significant number of these ions were found in the space surrounding Mercury, scientists have suggested that they were formed from water molecules destroyed on the surface or in the exosphere of the planet by the solar wind.

On February 5, 2008, a group of astronomers from Boston University led by Jeffrey Baumgardner announced the discovery of a comet-like tail off the planet Mercury with a length of more than 2.5 million km. Found it during observations from ground-based observatories in the sodium line. Before that, it was known about a tail no more than 40,000 km long. The group's first image was taken in June 2006 with the United States Air Force's 3.7-meter telescope on Mount Haleakala, Hawaii, followed by three more smaller instruments, one at Haleakala and two at McDonald Observatory, Texas. A 4-inch (100 mm) telescope was used to create an image with a large field of view. The image of the long tail of Mercury was captured in May 2007 by Jody Wilson (Senior Scientist) and Karl Schmidt (Graduate Student). The apparent length of the tail for an observer from Earth is about 3 °.

New data on the tail of Mercury appeared after the second and third flyby of the Messenger in early November 2009. Based on this data, NASA employees were able to propose a model for this phenomenon.

Features of observation from Earth

The apparent magnitude of Mercury ranges from -1.9 to 5.5, but it is not easy to see due to its small angular distance from the Sun (maximum 28.3 °). At high latitudes, the planet can never be seen in the dark night sky: Mercury is visible for a very short time after dusk. The optimal time for observing the planet is morning or evening twilight during the periods of its elongations (periods of the maximum distance of Mercury from the Sun in the sky, occurring several times a year).

The most favorable conditions for observing Mercury are at low latitudes and near the equator: this is due to the fact that the duration of twilight is the shortest there. It is much more difficult to find Mercury in mid-latitudes and is possible only during the period of the best elongations, and in high latitudes it is impossible at all. The most favorable conditions for observing Mercury in the middle latitudes of both hemispheres are around the equinoxes (the duration of twilight is minimal).

The earliest known observation of Mercury was recorded in the tables "Mul apin" (a collection of Babylonian astrological tables). This observation was most likely made by Assyrian astronomers around the 14th century BC. e. The Sumerian name used for Mercury in the Mul apin tables can be transcribed as UDU.IDIM.GUU4.UD (jumping planet). Initially, the planet was associated with the god Ninurta, and in later records it is called "Naboo" in honor of the god of wisdom and scribal art.

IN Ancient Greece at the time of Hesiod, the planet was known under the names ("Stilbon") and ("Hermaon"). The name "Hermaon" is a form of the name of the god Hermes. Later, the Greeks began to call the planet "Apollo".

There is a hypothesis that the name Apollo corresponded to the visibility in the morning sky, and Hermes (Hermaon) in the evening sky. The Romans named the planet after the swift-footed god of commerce Mercury, who is equivalent to the Greek god Hermes, because he moves across the sky faster than other planets. The Roman astronomer Claudius Ptolemy, who lived in Egypt, wrote about the possibility of moving a planet through the disk of the Sun in his work "Hypotheses about the planets." He suggested that such a passage had never been observed because a planet like Mercury was too small to observe, or because the moment of passage was infrequent.

IN Ancient China Mercury was called Chen-xing, "Morning Star". It was associated with the north direction, black and the water element in Wu Xing. According to the "Hanshu", the synodic period of Mercury was recognized by Chinese scientists as 115.91 days, and according to the "Hou Hanshu" - 115.88 days. In modern Chinese, Korean, Japanese and Vietnamese cultures, the planet has come to be called the "Water Star."

Indian mythology used the name Budha for Mercury. This god, the son of Soma, was dominant on Wednesdays. In Germanic paganism, God Odin was also associated with the planet Mercury and with the environment. The Maya Indians represented Mercury as an owl (or, perhaps, as four owls, with two corresponding to the morning appearance of Mercury, and two to the evening), which was the messenger of the afterlife. In Hebrew, Mercury was called "Koha in Hama".
Mercury on starry sky (above, above the Moon and Venus)

In the Indian astronomical treatise "Surya-siddhanta", dated by the 5th century, the radius of Mercury was estimated at 2420 km. The error is less than 1% compared to the true radius (2439.7 km). However, this estimate was based on an imprecise assumption about the planet's angular diameter, which was taken as 3 arc minutes.

In medieval Arab astronomy, the Andalusian astronomer Az-Zarqali described the deferent of the geocentric orbit of Mercury as an oval, like an egg or a pine nut. However, this conjecture had no effect on his astronomical theory and his astronomical calculations. In the XII century, Ibn Badja observed two planets in the form of spots on the surface of the Sun. Later, the astronomer of the Maragha observatory Al-Shirazi suggested that his predecessor observed the passage of Mercury and (or) Venus. In India, the astronomer of the Kerali school, Nilakansa Somayaji (English) Russian. in the 15th century he developed a partially heliocentric planetary model in which Mercury revolved around the Sun, which, in turn, revolved around the Earth. This system was similar to that of Tycho Brahe, developed in the 16th century.

Medieval observations of Mercury in the northern parts of Europe were hampered by the fact that the planet is always observed at dawn - morning or evening - against the background of a twilight sky and rather low above the horizon (especially in northern latitudes). The period of its best visibility (elongation) occurs several times a year (lasting about 10 days). Even during these periods, it is not easy to see Mercury with the naked eye (a relatively dim star against a fairly light sky background). There is a story that Nicolaus Copernicus, who observed astronomical objects in the northern latitudes and the foggy climate of the Baltic States, regretted that he never saw Mercury in his entire life. This legend was formed on the basis that in the work of Copernicus "On rotations celestial spheres”Does not give a single example of observations of Mercury, but he described the planet using the results of observations of other astronomers. As he himself said, Mercury can still be "caught" from the northern latitudes, showing patience and cunning. Consequently, Copernicus could well observe Mercury and observed it, but he made a description of the planet according to other people's research results.

Observations with telescopes

The first telescopic observation of Mercury was made by Galileo Galilei in the early 17th century. Although he observed the phases of Venus, his telescope was not powerful enough to observe the phases of Mercury. In 1631, Pierre Gassendi made the first telescopic observation of the planet's passage across the solar disk. The moment of passage was calculated before by Johannes Kepler. In 1639, Giovanni Zupi discovered with a telescope that the orbital phases of Mercury are similar to those of the Moon and Venus. Observations have conclusively demonstrated that Mercury revolves around the Sun.

A very rare astronomical event is the overlap of one planet of the disk of another, observed from Earth. Venus overlaps Mercury once every several centuries, and this event was observed only once in history - on May 28, 1737 by John Bevis at the Royal Greenwich Observatory. Venus's next overlap of Mercury will be December 3, 2133.

The difficulties accompanying the observation of Mercury led to the fact that for a long time it was studied less than other planets. In 1800, Johann Schroeter, observing the details of the surface of Mercury, announced that he had observed mountains 20 km high on it. Friedrich Bessel, using Schroeter's sketches, mistakenly determined the rotation period around its axis at 24 hours and the axis tilt at 70 °. In the 1880s, Giovanni Schiaparelli mapped the planet more accurately and suggested that the rotation period is 88 days and coincides with the sidereal period of the revolution around the Sun due to tidal forces. The work on mapping Mercury was continued by Eugene Antoniadi, who in 1934 published a book that presented old maps and his own observations. Many details of the surface of Mercury are named after Antoniadi's maps.

Italian astronomer Giuseppe Colombo (English) Russian. noticed that the period of rotation is 2/3 of the sidereal period of rotation of Mercury, and suggested that these periods fall into the 3: 2 resonance. Data from "Mariner-10" subsequently confirmed this point of view. This does not mean that Schiaparelli and Antoniadi's maps are wrong. It's just that astronomers saw the same details of the planet every second revolution of it around the Sun, entered them on the maps and ignored observations at the time when Mercury was facing the Sun by the other side, since due to the geometry of the orbit at that time the conditions for observation were bad.

The closeness of the Sun creates some problems for telescopic studies of Mercury. For example, the Hubble telescope has never been used and will not be used to observe this planet. Its device does not allow observing objects close to the Sun - if you try to do this, the equipment will receive irreversible damage.

Research of Mercury by modern methods

Mercury is the least studied terrestrial planet. In the 20th century, the telescopic methods of studying it were supplemented by radio astronomy, radar and research using spacecraft. Radio astronomical measurements of Mercury were first carried out in 1961 by Howard, Barrett and Haddock using a reflector with two radiometers mounted on it. By 1966, on the basis of the accumulated data, good estimates of the temperature of the surface of Mercury were obtained: 600 K at the sun-point and 150 K on the unlit side. The first radar observations were carried out in June 1962 by V.A.Kotelnikov's group at IRE; they revealed the similarity of the reflective properties of Mercury and the Moon. In 1965, similar observations with the Arecibo radio telescope made it possible to estimate the rotation period of Mercury: 59 days.

Only two spacecraft were sent to explore Mercury. The first was Mariner 10, which flew past Mercury three times in 1974-1975; the maximum approach was 320 km. As a result, several thousand images were obtained, covering approximately 45% of the planet's surface. Further studies from Earth have shown the possibility of water ice in polar craters.

Of all the planets visible to the naked eye, only Mercury never had its own artificial satellite... NASA is currently on a second mission to Mercury, called Messenger. The device was launched on August 3, 2004, and in January 2008 it first flew around Mercury. To enter orbit around the planet in 2011, the device made two more gravitational maneuvers near Mercury: in October 2008 and in September 2009. The Messenger also performed one gravity assist near Earth in 2005 and two maneuvers near Venus: in October 2006 and in June 2007, during which it checked the equipment.

Mariner 10 - the first spacecraftwho reached Mercury.

The European Space Agency (ESA), together with the Japanese Aerospace Research Agency (JAXA), is developing the Bepi Colombo mission, which consists of two spacecraft: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO). The European MPO will explore the surface of Mercury and its depths, while the Japanese MMO will observe the magnetic field and magnetosphere of the planet. The BepiColombo launch is planned for 2013, and in 2019 it will enter orbit around Mercury, where it will split into two components.

The development of electronics and computer science has made it possible for ground-based observations of Mercury using CCD radiation receivers and subsequent computer processing of images. One of the first series of observations of Mercury with CCD receivers was carried out in 1995-2002 by Johan Varell at the observatory on the island of La Palma using a half-meter solar telescope. Varell selected the best of the images without using computerized data. The reduction began to be applied at the Abastumani Astrophysical Observatory to the series of photographs of Mercury obtained on November 3, 2001, as well as at the Skinakas Observatory of the Heraklion University for the series dated May 1-2, 2002; to process the observation results, the method of correlation combination was used. The resulting resolved image of the planet was similar to the Mariner-10 photomosaic, the outlines of small formations 150-200 km in size were repeated. This is how the map of Mercury was compiled for longitudes 210-350 °.

On March 17, 2011, the Messenger interplanetary probe entered the orbit of Mercury. It is assumed that with the help of the equipment installed on it, the probe will be able to explore the landscape of the planet, the composition of its atmosphere and surface; also the equipment of "Messenger" allows to conduct research of energetic particles and plasma. The service life of the probe is one year.

On June 17, 2011 it became known that, according to the data of the first studies carried out by the Messenger spacecraft, the planet's magnetic field is not symmetrical about the poles; thus, different numbers of solar wind particles reach the north and south poles of Mercury. An analysis of the prevalence of chemical elements on the planet.

Features of the nomenclature

The rules for naming geological objects on the surface of Mercury were approved at the XV General Assembly of the International Astronomical Union in 1973:
Small crater Hun Kal (indicated by an arrow), which serves as an anchor point for the system of longitudes of Mercury. Photo of AMS "Mariner-10"

The largest object on the surface of Mercury, with a diameter of about 1300 km, is called the Plain of Heat, since it is located in the region of maximum temperatures. It is a multi-ring structure of impact origin, filled with solidified lava. Another plain, located in the region of minimum temperatures, y north pole, called the Northern Plain. The rest of these formations were called the planet Mercury or the analogue of the Roman god Mercury in languages different nations the world. For example: Plain Suisei (planet Mercury in Japanese) and Plain Budha (planet Mercury in Hindi), Plain Sobkou (planet Mercury among the ancient Egyptians), Plain Odin (Scandinavian god) and Plain Tyr (ancient Armenian deity).
The craters of Mercury (with two exceptions) are named after famous people in the humanitarian sphere of activity (architects, musicians, writers, poets, philosophers, photographers, artists). For example: Barma, Belinsky, Glinka, Gogol, Derzhavin, Lermontov, Mussorgsky, Pushkin, Repin, Rublev, Stravinsky, Surikov, Turgenev, Feofan Grek, Fet, Tchaikovsky, Chekhov. The exceptions are two craters: Kuiper, named after one of the main developers of the Mariner 10 project, and Hun Kal, which means the number “20” in the language of the Mayan people, who used the decimal number system. The last crater is located at the equator at meridian 200 west longitude and was chosen as a convenient reference point for reference in the coordinate system of the surface of Mercury. Initially, the larger craters were assigned the names of celebrities who, according to the IAU, were correspondingly more important in world culture. The larger the crater, the stronger the influence of the personality on modern world... The top five included Beethoven (643 km in diameter), Dostoevsky (411 km), Tolstoy (390 km), Goethe (383 km) and Shakespeare (370 km).
Escarpas (ledges), mountain ranges and canyons are named after the ships of the explorers who went down in history, since the god Mercury / Hermes was considered the patron saint of travelers. For example: Beagle, Zarya, Santa Maria, Fram, Vostok, Mirny). The exceptions to the rule are two ridge named after the astronomers Ridge Antoniadi and Ridge Schiaparelli.
Valleys and other features on the surface of Mercury are named after major radio observatories in recognition of the importance of radar in planetary exploration. For example: Highteck Valley (radio telescope in the USA).
Subsequently, in connection with the opening in 2008 of an automatic interplanetary station "Messenger" of the furrows on Mercury, a rule for naming the furrows, which are named after great architectural structures, has been added. For example: The Pantheon in the Plain of Heat.

\u003e\u003e Rotation of Mercury

Features: rotation of Mercury around the Sun: speed, period, how much time the planet spends in orbit in the solar system, the length of the day and year from the photo.

Of all planets, motion and period rotation of Mercury is the most unusual. The fact is that the process of axial revolutions itself is slow. If the axis of rotation of Mercury takes 175.97 days, then it takes 88 days to fly around the orbit around the Sun. That is, the day lasts 1.999 times more than a year. Equatorial speed indicator - 10.892 km / h. It leads to sunny dayswhere 58.647 days are spent on turnover.

If you were visiting the planet, you would be able to observe how the sun rises to half and lingers at one point throughout the day. This happens 4 days before the moment of perihelion due to the fact that the orbital speed exceeds the angular one, and the star starts the reverse motion.

Rotation of Mercury around the Sun

Let's take a closer look at the rotation of Mercury around the Sun. During one of the Mercurian years, the average solar movement reaches two degrees a day in a westerly direction, due to which the day is three times longer than the rotation. The movement will change depending on the year. And the moment of aphelion it will slow down and give 3 degrees per day. But the Sun will also slow down and suspend its shift to the west, move east and return to the west again. The tilt of Mercury's rotation axis is shown below.

It should be understood that at the moment of a change in solar velocity, the star will increase in observable dimensions and then decrease.

The peculiarities and speed of rotation of the planet were not known until 1965. Then it was believed that everything depends on the planetary tides to the Sun. The breakthrough was made by Soviet researchers, who in 1962 managed to beat off radio signals from the surface of Mercury. Later, the Americans used Arecibo and confirmed the results, as well as a rotation period of 58.647 days.

Mercury is the closest planet to the Sun.
This planet got its name in honor of the god Mercury - the messenger of the gods, the patron saint of trade and travelers - because of its high speed of rotation around the Sun.
Mercury moves faster than all planets - 174,000 km / h.
It makes a complete revolution around the Sun in 88 (87.97) Earth days in an elongated orbit, sometimes moving away from the Sun by 70 million km, while the smallest distance to the Sun is 46 million km.

And the duration of a sidereal day on Mercury (one revolution around its axis) is 58.65 Earth days.
Rushing fast in orbit, Mercury turns lazily on its axis. In one Mercurian year, the planet manages to turn around its axis by one and a half revolutions.

The average time interval between the two upper climaxes of the Sun on this planet is 176 days. Interestingly, when it is near perihelion (the closest distance from the Sun), the Sun for an observer on the planet's surface can move in the opposite direction for 8 days.

Distance from Mercury to Earth varies from 82 to 217 million km.
The planet is visible to the naked eye.
In a few days, when viewed from Earth, Mercury changes its position relative to the Sun from the west (morning visibility) to the east (evening visibility).

The axis of rotation of Mercury and its orbit is practically perpendicular.
Mercury is so small that its mass (3.3 1023 kg) is 1/20 of the Earth's mass.
The radius of Mercury is only 2439.7 ± 1.0 km, which is less than the radius of Jupiter's satellite Ganymede and Saturn's satellite Titan.
The proximity to the Sun and the rather slow rotation of the planet, as well as the extremely rarefied atmosphere, lead to the fact that the sharpest temperature changes in the Solar System are observed on Mercury.
The temperature on the sunny side of the planet is 420 ° C.
The temperature on the dark side drops to -190 ° C.
The average density of Mercury is 5.43 g / cm³ (slightly less than the density of the Earth). This density indicates an increased content of metals in its depths.
The planet is almost spherical. Free fall acceleration on its surface is g \u003d 3.72 m / s2.

Mercury, along with Venus, Earth and Mars, belongs to the terrestrial planets.

When the Mariner 10 spacecraft transmitted the first close-up images of Mercury, astronomers threw up their hands: there was a second moon in front of them! The surface of Mercury turned out to be dotted with a grid of craters of various sizes, just like the surface of the Moon. Their size distribution was also similar to the lunar one. Most of the craters were formed by falling meteorites.
Mercury is very similar to the Moon.
It turned out that on Mercury, like on the Moon, there are two main types of terrain - analogs of lunar continents and seas. The mainland regions are the most ancient geological formations of Mercury, consisting of areas dotted with craters, mountainous and hilly formations, inter-crater plains. Analogues of the lunar seas are the smooth plains of Mercury, which are younger in age than the continents, somewhat darker than the continental formations, but still not as dark as the lunar seas and there are much less of them than on the Moon. Such areas on Mercury are concentrated in the area of \u200b\u200bthe Zhary plain - (diameter 1300 km).

Pictures and Map of Mercury

Video

So, what is the planet Mercury and what is so special about it that distinguishes it from other planets? Probably, first of all, it is worth listing the most obvious that can be easily gleaned from various sources, but without which it will be difficult for a person to make a big picture.

At the moment (after Pluto was "demoted" to dwarf planets), Mercury is the smallest of the eight planets in our solar system. Also, the planet is located at the closest distance to the Sun, and therefore makes a revolution around our star much faster than other planets. Apparently, it was the last quality that served as a reason to name her in honor of the most fleeting messenger of the Gods named Mercury, an extraordinary character from legends and myths Ancient Romewith phenomenal speed.

By the way, it was the ancient Greek and Roman astronomers who more than once called Mercury both the “morning” and “evening” star, although most of them knew that both names correspond to the same space object. Even then, the ancient Greek scientist Heraclitus pointed out that Mercury and Venus rotate around the Sun, and not around.

Mercury today

Nowadays, scientists know that due to the close proximity of Mercury to the Sun, the temperature on its surface can reach up to 450 degrees Celsius. But the absence of an atmosphere on this planet does not allow Mercury to retain heat, and on the shadow side, the surface temperature can drop sharply to 170 degrees Celsius. The maximum temperature difference during the day and at night on Mercury was the highest in the solar system - more than 600 degrees Celsius.

In size, Mercury is a little bigger than the moon, but at the same time much heavier than our natural satellite.

Despite the fact that the planet has been known to people since time immemorial, the first image of Mercury was obtained only in 1974, when the Mariner 10 spacecraft transmitted the first images on which it was possible to make out some of the relief features. After that, a long-term active phase began to study this cosmic body, and after several decades, in March 2011, a spacecraft called Messenger reached the orbit of Mercury. after which, finally, mankind received answers to many questions.

The atmosphere of Mercury is so thin that it practically does not exist, and the volume is about 10 to the fifteenth power of times less than the dense layers of the Earth's atmosphere. At the same time, the vacuum in the atmosphere of this planet is much closer to the true vacuum, if we compare it with any other vacuum created on Earth by means of technical means.

There are two explanations for the absence of an atmosphere on Mercury. First, it is the density of the planet. It is believed that with a density of only 38% of the Earth's density, Mercury simply cannot preserve most of the atmosphere. Secondly, the proximity of Mercury to the Sun. Such a close distance to our star makes the planet most susceptible to influence solar windsthat sweep away the last remnants of what might be called the atmosphere.

Nevertheless, no matter how meager the atmosphere on this planet is, it still exists. According to the NASA space agency, according to its chemical composition, it consists of 42% oxygen (O2), 29% sodium, 22% hydrogen (H2), 6% helium, 0.5% potassium. The rest of the insignificant part is made up of molecules of argon, carbon dioxide, water, nitrogen, xenon, krypton, neon, calcium (Ca, Ca +) and magnesium.

It is believed that the rarefaction of the atmosphere is due to the presence of extreme temperatures on the planet's surface. The lowest temperature can be about -180 ° C, and the highest is about 430 ° C. As mentioned above, Mercury has the largest surface temperature range of any planet in the solar system. The extreme maxima present on the side facing the Sun are precisely the result of an insufficient atmospheric layer that is unable to absorb solar radiation. Incidentally, the extreme cold on the planet's shadow side is due to the same. The absence of a significant atmosphere does not allow the planet to retain solar radiation and heat very quickly leaves the surface, freely leaving into outer space.

Until 1974, the surface of Mercury remained largely a mystery. Observations of this cosmic body from Earth were very difficult due to the planet's proximity to the Sun. It was possible to consider Mercury only before dawn or immediately after sunset, but on Earth at this time the line of sight is significantly limited by the too dense layers of the atmosphere of our planet.

But in 1974, after a magnificent triple flyby of the Mariner 10 spacecraft on the surface of Mercury, the first sufficiently clear photographs of the surface were obtained. Surprisingly, despite significant time constraints, almost half of the entire surface of the planet was photographed during the Mariner 10 mission. As a result of the analysis of observational data, scientists were able to identify three essential features of the surface of Mercury.

The first feature is the huge number of impact craters that gradually formed on the surface over billions of years. The so-called Caloris basin is the largest of the craters, with a diameter of 1,550 km.

The second feature is the presence of plains between the craters. It is believed that these smooth surface areas were created by the movement of lava flows around the planet in the past.

And, finally, the third feature is the rocks scattered over the entire surface and reaching from several tens to several thousand kilometers in length and from one hundred meters to two kilometers in height.

Scientists especially emphasize the contradiction between the first two features. The presence of lava fields indicates that active volcanic activity was once present in the planet's historical past. However, the number and age of the craters, on the contrary, suggest that Mercury has been geologically passive for a very long time.

But the third is no less interesting. distinctive feature surface of Mercury. It turned out that the hills are formed by the activity of the planet's core, as a result of which the so-called "bulging" of the crust occurs. Such buckling on Earth is associated, as a rule, with the displacement of tectonic plates, while the loss of stability of the Mercury crust occurs due to the contraction of its core, which gradually shrinks. The processes occurring with the core of the planet lead to the contraction of the planet itself. The latest calculations by scientists indicate that the diameter of Mercury has decreased by more than 1.5 kilometers.

Structure of mercury

Mercury is made up of three distinct layers: crust, mantle, and core. The average thickness of the planet's crust, according to various estimates, ranges from 100 to 300 kilometers. The presence of the previously mentioned protuberances on the surface, which in their shape resemble those of the earth, indicates that, despite the sufficient hardness, the crust itself is very fragile.

The approximate thickness of Mercury's mantle is about 600 kilometers, which suggests that it is relatively thin. Scientists believe that it was not always so thin and in the past there was a collision of the planet with a huge planetesmial, which led to the loss of a significant mass of the mantle.

The core of Mercury has become the subject of many studies. It is believed to be 3,600 kilometers in diameter and has some unique properties. Most interesting property is its density. Considering that the planetary diameter of Mercury is 4878 kilometers (it is smaller than the satellite of Titan, whose diameter is 5125 kilometers and the satellite of Ganymede with a diameter of 5270 kilometers), the density of the planet itself is 5540 kg / m3 with a mass of 3.3 x 1023 kilograms.

So far, there is only one theory that has tried to explain this feature of the planet's core, and has cast doubt on the fact that the core of Mercury is actually solid. Having measured the features of the rebound of radio waves from the planet's surface, a group of planetary scientists came to the conclusion that the planet's core is actually liquid, and this explains a lot.

Orbit and rotation of Mercury

Mercury is much closer to the Sun than any other planet in our system and, accordingly, it takes the shortest time to orbit. A year on Mercury is only about 88 Earth days.

An important feature of the orbit of Mercury is its high eccentricity compared to other planets. Also, of all planetary orbits, Mercury's orbit is the least circular.
This eccentricity, along with the absence of a significant atmosphere, explains why the surface of Mercury has the widest range of extreme temperatures in the solar system. Simply put, the surface of Mercury heats up much more when the planet is at perihelion than at aphelion, since the difference in distance between these points is too great.

The orbit of Mercury itself is an excellent example of one of the leading processes in modern physics. This is a process called precession, which explains the displacement of Mercury's orbit relative to the Sun over time.

Despite the fact that Newtonian mechanics (i.e. classical physics) predicts the rates of this precession in great detail, the exact values \u200b\u200bhave not been determined. This became a real problem for astronomers in the late nineteenth and early twentieth centuries. Many concepts have been drawn up to explain the difference between theoretical interpretations and actual observations. According to one of the theories, it has even been suggested that there is an unknown planet whose orbit is closer to the Sun than Mercury.

However, the most plausible explanation came after Einstein's general theory of relativity was published. Based on this theory, scientists were finally able to accurately describe the orbital precession of Mercury.

Thus, for a long time it was believed that the spin-orbit resonance of Mercury (the number of revolutions in orbit) was 1: 1, but, in the end, it was proved that in fact it is 3: 2. It is thanks to this resonance that a phenomenon is possible on the planet that is impossible on Earth. If the observer was on Mercury, he would be able to see that the Sun rises to the highest point in the sky, and then “turns on” the reverse motion and descends in the same direction from which it rose.

1. Mercury has been known to mankind since ancient times. Despite the fact that the exact date of its discovery is unknown, the first mention of the planet is believed to have appeared around 3000 BC. among the Sumerians.
2. A year on Mercury is 88 Earth days, but a Mercury day is 176 Earth days. Mercury is almost completely blocked by the Sun by tidal forces, but over time it slowly rotates the planet around its axis.
3. Mercury revolves so quickly around the Sun that some early civilizations believed they were actually two different stars, one of which appears in the morning and the other in the evening.
4. With a diameter of 4.879 km, Mercury is the smallest planet in the solar system, and is also one of the five planets that can be seen in the night sky with the naked eye.
5. After Earth, Mercury is the second densest planet in the solar system. Despite its small size, Mercury is very dense, as it consists mainly of heavy metals and stone. This allows us to attribute it to the terrestrial planets.
6. Astronomers didn't realize that Mercury was a planet until 1543, when Copernicus created a heliocentric model of the solar system, according to which the planets rotate around the sun.
7. The planet's gravitational forces are 38% of gravitational forces Earth. This means that Mercury is unable to hold the atmosphere that it has, and that that remains is blown away by the solar wind. Nevertheless, all the same solar winds attract gas particles, dust from micrometeorites to Mercury and form radioactive decay, which in some way forms the atmosphere.
8. Mercury has no moons or rings due to its low gravity and lack of atmosphere.
9. There was a theory that between the orbits of Mercury and the Sun there is an undiscovered planet Vulcan, but its presence has not been proven.
10. Mercury's orbit is an ellipse, not a circle. It has the most eccentric orbit in the solar system.
11. Mercury is only the second highest temperature among the planets in the solar system. First place is

The planets of the solar system

According to official position The International Astronomical Union (IAS), an organization that assigns names to astronomical objects, has a total of 8 planets.

Pluto was excluded from the category of planets in 2006. since in the Kuiper belt there are objects that are larger / or equal in size to Pluto. Therefore, even if it is taken for a full-fledged celestial body, then it is necessary to add Eris to this category, which has almost the same size with Pluto.

As defined by MAC, there are 8 known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

All planets are divided into two categories depending on their physical characteristics: the terrestrial group and the gas giants.

Schematic representation of the location of the planets

Terrestrial planets

Mercury

The smallest planet in the solar system has a radius of only 2,440 km. The period of revolution around the Sun, for ease of understanding, equated to the Earth's year, is 88 days, while Mercury manages to complete a revolution around its own axis only one and a half times. Thus, his day lasts approximately 59 Earth days. For a long time it was believed that this planet was all the time turned to the Sun by the same side, since the periods of its visibility from the Earth were repeated with a frequency approximately equal to four Mercury days. This misconception was dispelled with the advent of the possibility of using radar research and conducting continuous observations using space stations. The orbit of Mercury is one of the most unstable, changing not only the speed of movement and its distance from the Sun, but also the position itself. Anyone interested can observe this effect.

Mercury in color, image from MESSENGER spacecraft

The proximity to the Sun has caused Mercury to experience the largest temperature fluctuations among the planets of our system. The average daytime temperature is about 350 degrees Celsius, and the nighttime temperature is -170 ° C. Sodium, oxygen, helium, potassium, hydrogen and argon were found in the atmosphere. There is a theory that he was previously a satellite of Venus, but so far this remains unproven. Own satellites he is missing.

Venus

The second planet from the Sun, the atmosphere of which is almost entirely carbon dioxide. It is often called the Morning Star and the Evening Star, because it is the first of the stars that becomes visible after sunset, just as before dawn it continues to be visible even when all other stars have disappeared from sight. The percentage of carbon dioxide in the atmosphere is 96%, nitrogen in it is relatively small - almost 4%, and water vapor and oxygen are present in very small quantities.

Venus in the UV spectrum

This atmosphere creates a greenhouse effect, the surface temperature is therefore even higher than that of Mercury and reaches 475 ° C. It is considered the most leisurely, the Venusian day lasts 243 Earth days, which is almost equal to a year on Venus - 225 Earth days. Many call it the sister of the Earth because of its mass and radius, the values \u200b\u200bof which are very close to those on Earth. The radius of Venus is 6052 km (0.85% of the Earth). There are no satellites, like Mercury.

The third planet from the Sun and the only one in our system where there is liquid water on the surface, without which life on the planet could not have developed. At least life is as we know it. The radius of the Earth is 6371 km and, unlike other celestial bodies of our system, more than 70% of its surface is covered with water. The rest of the space is occupied by continents. Another feature of the Earth is the tectonic plates hidden under the planet's mantle. At the same time, they are able to move, albeit at a very low speed, which over time causes a change in the landscape. The speed of the planet moving along it is 29-30 km / sec.

Our planet from space

One revolution on its axis takes almost 24 hours, and the full orbital passage lasts 365 days, which is much longer in comparison with the nearest neighboring planets. The Earth's day and year are also taken as a standard, but this was done only for the convenience of perception of time intervals on the other planets. The Earth has one natural satellite - the Moon.

Mars

The fourth planet from the Sun, known for its tenuous atmosphere. Since 1960, Mars has been actively explored by scientists from several countries, including the USSR and the USA. Not all exploration programs have been successful, but water found at some sites suggests that primitive life on Mars exists, or has existed in the past.

The brightness of this planet allows you to see it from Earth without any instruments. Moreover, once every 15-17 years, during the Opposition, it becomes the brightest object in the sky, eclipsing even Jupiter and Venus.

The radius is almost half that of the Earth and is 3390 km, but the year is much longer - 687 days. He has 2 satellites - Phobos and Deimos .

An illustrative model of the solar system

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• The sun

  The sun is a star, which is a hot ball of incandescent gases at the center of our solar system. Its influence extends far beyond the orbits of Neptune and Pluto. Without the Sun and its intense energy and heat, there would be no life on Earth. There are billions of stars, like our Sun, scattered across the Milky Way galaxy.

• Mercury

  Scorched by the Sun, Mercury is only slightly larger than Earth's satellite Moon. Like the Moon, Mercury is practically devoid of an atmosphere and cannot smooth out the traces of impact from falling meteorites, therefore, like the Moon, it is covered with craters. The daytime side of Mercury gets very hot on the Sun, while on the night side the temperature drops hundreds of degrees below zero. There is ice in the craters of Mercury, which are located at the poles. Mercury makes one revolution around the Sun every 88 days.

• Venus

  Venus is a world of monstrous heat (even more than on Mercury) and volcanic activity. Similar in structure and size to Earth, Venus is covered in a thick and toxic atmosphere that creates a strong greenhouse effect. This scorched world is hot enough to melt lead. Radar images through the mighty atmosphere revealed volcanoes and warped mountains. Venus rotates in the opposite direction from the rotation of most planets.

• Earth is an ocean planet. Our home, with its abundance of water and life, makes it unique in our solar system. Other planets, including several moons, also have ice deposits, atmosphere, seasons and even weather, but only on Earth did all these components come together in such a way that life became possible.

• Mars

  Although details of the surface of Mars are difficult to see from Earth, telescope observations show that Mars has seasons and white spots at the poles. For decades, people believed that the bright and dark areas on Mars were patches of vegetation and that Mars might be a suitable place to live, and that water exists in the polar caps. When the spacecraft Mariner 4 flew off Mars in 1965, many of the scientists were shocked to see photographs of the gloomy planet covered in craters. Mars turned out to be a dead planet. Later missions, however, revealed that Mars holds many mysteries that still remain to be solved.

• Jupiter

  Jupiter is the most massive planet in our solar system with four large moons and many small moons. Jupiter forms a kind of miniature solar system. To turn into a full-fledged star, Jupiter had to become 80 times more massive.

• Saturn

  Saturn is the farthest of the five planets that were known before the invention of the telescope. Like Jupiter, Saturn is composed primarily of hydrogen and helium. Its volume is 755 times that of the Earth. Winds in its atmosphere reach speeds of 500 meters per second. These fast winds, combined with the heat rising from the planet's interior, are causing the yellow and golden streaks we see in the atmosphere.

• Uranus

  The first planet found with a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet is so far from the Sun that one revolution around the Sun takes 84 years.

• Neptune

  The distant Neptune revolves almost 4.5 billion kilometers from the Sun. It takes 165 years for one revolution around the Sun. It is invisible to the naked eye due to its great distance from Earth. Interestingly, its unusual elliptical orbit intersects with the orbit of the dwarf planet Pluto, which is why Pluto is inside the orbit of Neptune for about 20 years out of 248 during which it makes one revolution around the Sun.

• Pluto

  Tiny, cold and incredibly distant, Pluto was discovered in 1930 and has long been considered the ninth planet. But after the discoveries of Pluto-like worlds that were even further away, Pluto was transferred to the category of dwarf planets in 2006.

Planets are giants

There are four gas giants located beyond the orbit of Mars: Jupiter, Saturn, Uranus, Neptune. They are found in the outer solar system. They are distinguished by their massiveness and gas composition.

Planets solar system, not to scale

Jupiter

The fifth from the Sun and the largest planet in our system. Its radius is 69912 km, it is 19 times larger than the Earth and only 10 times smaller than the Sun. The year on Jupiter is not the longest in the solar system, it lasts 4333 Earth days (less than 12 years). His own day has a duration of about 10 Earth hours. The exact composition of the planet's surface has not yet been determined, but it is known that krypton, argon and xenon are present on Jupiter in much larger quantities than on the Sun.

It is believed that one of the four gas giants is actually a failed star. This theory is supported by the largest number of satellites, of which Jupiter has many - as many as 67. To imagine their behavior in the planet's orbit, a sufficiently accurate and precise model of the solar system is needed. The largest of them are Callisto, Ganymede, Io and Europa. At the same time, Ganymede is the largest satellite of the planets in the entire solar system, its radius is 2634 km, which is 8% larger than the size of Mercury, the smallest planet in our system. Io differs in that it is one of three satellites with an atmosphere.

Saturn

The second largest planet and the sixth in the solar system. Compared to other planets, the composition of chemical elements is most similar to the Sun. The radius of the surface is 57350 km, the year is 10 759 days (almost 30 Earth years). The day here lasts a little longer than on Jupiter - 10.5 Earth hours. By the number of satellites, it is not much behind its neighbor - 62 against 67. The largest satellite of Saturn is Titan, just like Io, which has an atmosphere. Slightly smaller in size, but no less famous from this - Enceladus, Rhea, Dione, Tethys, Iapetus and Mimas. It is these satellites that are objects for the most frequent observation, and therefore we can say that they are the most studied in comparison with the rest.

For a long time, rings on Saturn were considered a unique phenomenon inherent only in him. It has only recently been found that rings are present in all gas giants, but in others they are not so clearly visible. Their origin has not yet been established, although there are several hypotheses about how they came about. In addition, quite recently it was discovered that Rhea, one of the satellites of the sixth planet, also possesses a kind of rings.